And we shouldn't allow this concept to go unchallenged here on Lemmy.
Commenting on an active post is not brigading
Posting a link to something is not brigading
Commenting on something you were linked to is not brigading
The only thing that might be brigading, but isn't because it isn't a real thing, is someone explicitly going, "Hey everyone, go here and harass this person"
It's all fine and good that we have some new rules to keep the peace with other instances but we must fight against 
Their culture is so snarky and anti-collaboration, they get pissy with each other nearly as much as they do with us, and they don't engage any differently in either case. I really do feel bad for these people who are trapped in the atomized, all against all social paradigm of the new internet.
So much of the 'brigading' is just comrades pointing out and challenging racism or bigotry and agreeing that a reactionary is racist or bigoted. I think its this kind of collaboration that comes off as so offensive to them sometimes; it's not something that any of us have to argue about, so it might always come off as co-ordinated to those who are used to saying whatever tf they like without consequence. Must be strange to be challenged when it's acceptable to be a a conservative or a 'progressive' and a POS throughout most of the western world.